Air propellef



July 17, 1923; 1,461,866

C. DORNIER AIR PROPELLER Filed. June 28 1920 Jim Fla

INvENmR:

meme July 17,1923.

-. STATES cnaunn noamna, or rnmnmcnsnarmr, GERMANY, assrenoa, w mm:assrenmums, 'ro DOBNIEB-METALLBAUTEN- GESELLSCHAFT MIT BESCHB'A'NK'I'ER-m- PATENT OFFICE.

' TUNG AND CLAUDIUS DORINIER, OR FBIEDRICHSHAFEN, A. 3., GERMANY.

Am raornnrinr.

Application filed June 28, 1920. Serial 'No. 892,559. I (GRANTED UNDER.THE PROVISIONS OF THE A01 OF MARCH 3, 1921, 41 STAT. I.., 1318.)

To all whom it may concern:

' Be it known that I, CLAUDE DonNmn, a citizen of the GermanEmpire,residing at F riedrichshafen, Germany, have invented 5 certain new anduseful Improvements in Air Propellers (for which I have filed anapplication in Germany Sept. 2, 1916), of which the following is aspecification.

My invention refers to airropellers with hollow blades. Such propel erscan be obtained by flattening by pressure a hollow tubular body at itsends after the manner of propeller blades and by developing the centeras the boss of the screw. The subsequent transformation of a. tubularbody into a two bladed screw, however, can only be achieved withdifiiculty' with the desired-accuracy. On the other hand propellers areknown in which the hollow blades are mounted on blade-supports fixed tothe boss of the screw. In this latter type of construct on, however,

danger of the blades being hurled off by the centrifugal force. It' isthe object of to avoid the drawbacks of both types of construction. Thisaim isachie'ved by the propeller being composed of several interiorandexterior parts stretchin at least approximately from one blade e geto the other and by the blade laminations as well as the armsbeing-utilized as supporting parts.

Accordingly the object of the invention consists in an air-propellerwith hollow blades in which two blade laminations stretchingcontinuously from one blade edge to the other, and several pairs ofstays or rolled section girders also stretching from end to end, areemployed. Accordin to-the invention the section girders situate on theoutside, at the same time, serve as transition bodies 'for thetransition from one blade lamination to theother; In this manner greatstrength of the finished propeller can be achieved .with easymanufacturing and great accuracy of the va ious parts. The manufacture:of an air-propeller be"- comes particularly advantageous, if the.

parts of the blades situated outside the inner pair of stays are madelighter than the parts. inside .ithe pair of stays. As the middle partof the propeller which is stayed there exists the my present inventionby D the girders, possesses great strength owing to its box 'gi rdersshape, the blade ends which are not fastened together yet, can be bentup elastically a little without difliculty, thereby rendering the inner,stays easily accessible for riveting tools, etc. Besides, the bladebecomes lighter.

The drawing attached to this specification and forming part thereof,illustrates an ex ample of a modification of the present invention in apurely diagrammatical manner.

' sists of the boss of the screw, a suction and a pressure bladelamination continuous in both cases, the inner'stays, the outer stays'and two boom butt straps.

Manufacture can take place in the following manner: First the bosses ofthe screws are riveted to ether with the two inner stays and each ladewith the pertinent boom butt strap. Thereupon the one to the boss ofblade lamination is riveted the screw as well as the flanges of the contnuous inner stays. Then the second blade is riveted on. whilst holdin uptakes place from the sides or the en s. Finally the outer stays ,areriveted in. For these the rivets are riveted right through, whilst forthe inner stays the rivets'only connect one blade lamination to thesupporting stay flan e at a time,

ostly the pressure side will be plane or only slightly vaulted. Thepressure blade lamination can therefore be bent up during the rivetingbeginning from the boss of the screw, thus enabling specially easyholding- 'up. It is useful to make the blade laminations and stays oflight metal, whilst steel ispreferable for the boss of the screw. Thethickness of the blades can decrease from the boss of the-screw towardsthe points. It is advisable to give the inner staysa U- shapedcross-section with the flanges pointing outwards. In the case of verylarge p can be employed.

. dimensions compound sections or box beam sections may also beemployed. -Th e rivet heads on the outer surface must be countersunk.,The boom butt straps can also be left 6 out. A special. advantage ofthis construction lies in the fact that small screw bosses I claim 1 Ina hollow propeller in eombinatiom. l0 two metal plates suitabl K edgesand extending eac from the outer united at their end of one blade to theouter end of the other, and a plurality of channels inserted between andfixed to said blades and extending longitudinally thereof one end 5 tothe other.

inglongitudinally thereof from one'end to the other, the middle portionsof said plates being thicker than the portions adjoining :6 theirlongitudinal edges. v

In testimony whereof I aflix my signature.

CLAUDE DORNIER.

